The present invention relates generally to disk brakes, and refers more particularly to disk brakes which are usually fitted to industrial apparatus such as for example a travelling crane, for effecting the emergency stopping of an output shaft of a motor in the apparatus, or of a member fastened to the output shaft.
More precisely, the present invention relates to emergency brakes of this kind which comprise a frame, a rotating disk joined to the member which is to be braked, to brake shoes disposed one on each side of the disk, braking levers on which the shoes are articulated by pivots or pivot means and which are articulated to one another by pivots or pivot means, and an on/off control means acting on the braking levers and comprising resilient gripping means adapted to urge normally at least one of the braking levers in a direction corresponding to the gripping of the disk, and electromagnetic release means which, when operated, oppose the action of the gripping means.
A brake of this type is described in French Patent No. 1,476,750 and also in the first Patent of Addition thereto, No. 91440.
Because of its construction, a brake of this kind is not capable of progressive action, so that in cases where it is desirable to be able to effect progressive braking of the disk, it is usual to associate with it a second brake disposed in parallel and operable on the same disk for effecting progressive deceleration in the usual manner.
This arrangement thus requires the utilisation of two separate brakes on the same disk.
Apart from the fact that this arrangement is expensive, it is not always possible for reasons of space.
In order to overcome this disadvantage, it has already been proposed in French Patent No. 1,563,082 to equip the brake in question with a dual control system, that it to say to provide it, in parallel with its on/off control means, with a progressively acting control means adapted to act on one of the brake levers with which it is equipped, in a direction corresponding to the gripping of the disk in question.
However, in the practical embodiments proposed for this purpose in the aforesaid patent, which are satisfactory in most applications and which in particular have the advantage of enabling the effects of the two control means to be added together if desired, the progressively acting control means is a hydraulic control means in order to limit as much as possible the lateral dimension of the unit, so that for the operation of the brake in question it is necessary to provide on the one hand electric cables capable of supplying the electromagnetic release means provided in the on/off control means, and in addition piping capable of supplying fluid under pressure to the progressively acting control means.
For certain applications, and particularly in the case of travelling cranes, the presence of piping of this kind may be awkward and dangerous, and/or the response time of the corresponding control may be too long.
The main object of the present invention is to provide various improvements to disk brakes of the kind concerned which minimise or avoid these disadvantages.